What do you know about...

[aeronyx]

MD5 spoofing?

If you've heard, as of recently, Nexon has 'patched' REZ modding for Combat Arms with a MD5 Hash check on the game files.

When you mod a file, its hash changes, etc, so I want to know about modifying a file's MD5 hash/checksum to bypass this.

:x

/discuss

[-Raz0r-]

The MD5 hash will be calculated at runtime. It's not stored inside the file itself.
You'll have to modify the process that calculates the hash to bypass the check. Either return a false hash, or skip the verification routine altogether. I don't know how possible this will be, I'm not familiar with Nexon or CA.

An unrealistic approach would be to find a hash collision, but this will prove to be much more work than the benefit.

[Jason]

Finding a collision isn't a solution to the problem at all. Unless by some 1/100000000000000000000000000 chance the modifications you make when modding SOMEHOW collide with what the original file's MD5 was, otherwise it's useless. The only sensible way would be to hook/patch the verification method and just return true all the time.

[.::SCHiM::.]

You can't 'spoof' md5, integrity is one of the reasons md5 exists at all. Hash collisions are of no use, they are only useful when you want to bypass password checks. As everyone here suggested, hook the verify function. Or inject your maps at runtime.

[Hell_Demon]

Make a copy of the original files in a folder named Original > Redirect all open/read/write calls to the original files > profit.